Composition for use in solvent extraction process for the recovery of uranium and rare earth metals from aqueous solutions



United States Patent COMPGSITEON Fflli USE IN SOLVENT EXTRAC- TIONPROCESS FOR THE RECOVERY Oi URA- NIUM AND RARE EARTH NETALS FROM AQUE-OUS SULUTEONS Hamish Small, Midland, Mich, assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware No Drawing. Originalapplication Mar. 23, 1959, Ser. No. 801,164, new Patent No. 3,102,782,dated Sept. 3, 1963. Divided and this application Mar. 4, 1963, Ser.

4 Claims. (Cl. 260-22) The invention relates to the recovery of heavymetal values from aqueous solutions, and particularly to the recovery ofuranium and/ or rare earth metals, by solvent extraction. It relates,more particularly to compositions comprising an organic liquid solventor complexing agent for heavy metal values dissolved in awater-insoluble copolymer in particulate form and pertains especially toan improved process for the recovery of heavy metal values from aqueoussolutions by solvent extraction.

This application is a division of my copending application, Serial No.801,164, now Patent No. 3,102,782, entitled Solvent Extraction Processfor The Recovery of Uranium and Rare Earth Metals From AqueousSolutions, and filed March 23, 1959.

It is known to recover heavy metal values from aqueous solutions byextraction with a water-immiscible or a substantially water-immiscibleorganic solvent. For example, it has been proposed to extract uraniumvalues from aqueous solutions with diethyl ether, tributyl phosphate ora mixture of tributyl phosphate and kerosene or carbon tetrachloride.

It has also been proposed to recover heavy meal values from aqueoussolutions by dissolving an organic waterimmiscible complexing agent,e.g. tributyl phosphate in a molten wax such as petroleum wax orpolyethylene having a melting point between 200 and 220 F., cooling thesolution of the wax and the complexing agent, disintegrating the waxcomplex to a granular form and contacting the granular material with themetal-containing solution to be processed, whereby the metal values aretaken up by the wax-solvent complex.

However, the methods heretofore proposed for the recovery of heavy metalvalues from aqueous solutions have not been entirely satisfactorybecause an emulsion frequently forms during the contact of aqueous andorganic liquid media and phase separation becomes diflicult or sometimeseven impossible. The employing of the complexing agent dissolved in awax makes it difiicult to obtain good contact of the aqueous solutionwith the complexing agent dissolved in a wax makes it difficult toobtain good contact of the aqueous solution with the complexing agentbecause of the natural non-wettability of the wax.

It is an object of the invention to provide an improved process for therecovery of heavy metal values from aqueous solutions by solventextraction with new gel-like waterinsoluble solvent-containing resincompositions. Another object is to provide new compositions of mattercomprising water-insoluble gel-like solvent-containing alkenyl aromaticresin granules having good wettability and suitable for the recovery ofheavy metal values from aqueous solutions. Still another object is toprovide an improved process for the recovery of heavy metal values fromaqueous solutions wherein a small volume of liquid extractant containedin a permeable copolyrner matrix is employed to contact a relativelylarge volume of aqueous solution. Other and related objects may appearfrom the following description of the invention.

According to the invention the foregoing and related 3,145,213 PatentedAug. 25, 1964 objects are attained by bringing an aqueous solutioncontaining heavy metal values dissolved therein as solute into contactwith discrete granules of a cross-linked insoluble alkenyl aromaticresin consisting essentially of a copolymer of a predominant amount of amonoalkenyl aromatic hydrocarbon and a minor proportion of a divinylaromatic hydrocarbon, having on the surface of said copolymer granulessubstituent hydrophile groups of the formula SO X wherein X represents amember of the group consisting of hydrogen and a metal, which resingranules are swollen with an organic liquid comprising an organicwater-imrnisicible complexing agent or solvent for the heavy metalvalue, whereby the heavy metal values are rapidly and eificiently sorbedby the complexing agent in the resin granules, and after separating fromthe metaldepleted aqueous waste solution the heavy metal values arereadily eluted or extracted from the resin granules by washing them withWater or an aqueous solution.

The alkenyl aromatic resins to be employed in the process are thenormally hard insoluble cross-linked copolymers of one or moremonoalkenyl aromatic hydrocarbons having the general formula:

wherein Ar represents an aromatic hydrocarbon of the benzene series andR represents a member of the group consisting of hydrogen and the methylradical. Examples of suitable monoalkenyl aromatic hydrocarbons arestyrene, vinyltoluene, vinylxylene, ar-ethylvinylbenzene,isopropylstyrene, tert.-butylstyrene, ar-ethylvinyltoluene and the like.The copolymers contain from 92 to 99.5 percent by weight of one or moreof the monoalkenyl aromatic hydrocarbons chemically combined orinterpolymerized with from 8 to 0.5 percent by weight of a divinylaromatic hydrocarbon such as divinylbenzene, divinyltoluene,divinylxylene or the like. Such copolymers can be prepared in usual waysemploying procedures similar to those employed for the polymerization ofstyrene. For example, the copolymers can be prepared by polymerizing amixture of the monomers in mass, i.e. in the substantial absence of aninert solvent, or in an aqueous dispersion such as water or brine.Polymerization of the monomers while dispersed in an aqueous medium ispreferred since it affords ready control of the reaction and results inthe production of the copolymer in a granular or bead form.

The polymerization is accelerated by the use of a peroxy catalyst suchas benzoyl peroxide, tert.-butyl hydroperoxide, cumene peroxide,di-tert.-butyl peroxide, cumene hydroperoxide and the like, and isusually carried out at temperatures between about 60 and C. atatmospheric or superatmospheric pressure.

It is important that the granules of the alkenyl aromatic resin containon the surface thereof hydrophile groups of the formula SO X wherein Xrepresents a member of the group consisting of hydrogen and a metal,i.e. sulfonate groups such as the sulfonic acid group or a salt thereof,in an amount sufiicient to lend wettability to the resin granules byaqueous solutions, but insufficient to result in deleterious effects onthe resin granules such as cracking, breaking or spalling, when thegranules are subsequently swelled in an organic liquid such as a mixtureof a complexing agent and an inert solvent capable of swelling ordissolving polystyrene. The alkenyl aromatic resin granules can containsulfonate groups, preferably on the surface thereof in amountcorresponding to from 0.001 to 0.150 milliequivalent of hydrogen pergram of the dry resin granules. A lesser amount of sulfonate groupsresults in resin granules having poor Wettability with aqueous media,whereas greater amounts of the sulfonate groups, e.g. 0.21 sulfonategroup per gram of the dry resin, results in disintegration of the resingranules upon swelling in an organic liquid.

Surface sulfonation of the copolymer granules can be carried out byreacting the granular copolymer with sulfuric acid, chlorosulfonic acidor sulfur trioxide and at temperatures between about 20 and 100 C.depending for the most part upon the sulfonation agent employed, and inthe presence or absence of an inert diluent. A preferred method ofsurface sulfonating the copolymer granules is to suspend the copolymergranules in concentrated sulfuric acid, e.g. 98 percent sulfuric acid,and carry out the reaction at temperatures between 80 and 100 C.,suitably for a time of from about 1 to 120 minutes at atmosphericpressure or thereabout. Upon completing the sulfonating reaction thecopolymer is separated from the reaction mixture by filtering and iswashed with water and dried.

As complexing agents or solvents for the heavy metal values alkylphosphates show a preferred solubility for uranium values, and alkylphosphates containing from 4 to 8 carbon atoms in an alkyl group can beem loyed. Such alkyl phosphates have the general formula:

wherein R, R and R" independently represent an alkyl radical containingfrom 4 to 8 carbon atoms. Examples of suitable phosphates are tributylphosphate, trioctyl phosphate, trihexyl phosphate,tri-(2-ethylhexyl)phosphate, dibutylhexyl phosphate, dibutyloctylphosphate, dioctylbutyl phosphate or dihexylbutyl phosphate.

The alkyl phosphates are preferably employed in admixture with anorganic liquid solvent which is a swelling agent for the copolymer.Examples of suitable swelling agents are aromatic hydrocarbons such asbenzene, toluene, xylene, ethylbenzene, ethyltoluene, isopropylbenzene,or aliphatic chloroliydrocarbons, e.g. methylene chloride,perchloroethylene, trichloroethylene, carbon tetrachloride, chloroform,1,1,l-trichloroethane, ethylene dichloride, 1,1,2-trichloroethane,1,1,1,2-tetrachloroethane, or 1,1,2,2-tetrachloroethane. The swellingagent and the complexing agent can be used in proportions of from aboutto 89 percent by volume of the swelling agent and from 95 to 20 percentby volume of the complexing agent.

The copolymer granules containing hydrophile sulfonate groups can beimpregnated to form the gel-like solvent-containing compositions bysoaking the copolymer granules in a mixture of the alkyl phosphate andan organic swelling agent, e.g. toluene or perchloroethylene, ashereinbefore defined at between about 20 and 100 C. and at atmosphericpressure or thereabout. In a preferred procedure the copolymer granulesare suspended in a mixture of the alltyl phosphate, e.g. a mixture ofequal parts by volume of tributyl phosphate and perchloroethylene, untilswelled, then are transferred to a column and the solvent mixture ispassed through the bed of the resin granules until the er'liuent liquidis of substantially the same concentration as the feed liquid, whilemaintaining the copolymer and liquid mixture at elevated temperaturesbetween about 60 and 100 C. Such procedure results in rapidequilibration of the copolymer particles to form discrete gel-likesolvent-containing compositions. After equilibrating the copolymergranules with the solvent mixture the excess liquid is drained from theresin granules and they are washed with water. The gel-likesolvent-containing copolymer composition is then in a form suitable forthe recovery of heavy metal values from aqueous solutions, eg therecovery of uranyl nitrate from an aqueous solution containing the sameas solute.

The aqueous solutions to be treated in accordance with the invention canbe aqueous solutions of the salts of heavy metals such as uranium andthorium or salts of rare earth metals, and may be free from acid or maycontain free mineral acid such as nitric acid, sulfuric acid orhydrochloric acid, e.g. in a concentration up to about a S-normalaqueous solution of the acid, and may contain a salting-out agent, i.e.an inorganic compound which is highly soluble in water and which, whenadded in sufficient amounts to an aqueous salt solution to be extracted,promotes the interchange of the salt into an organic solvent therefor.The concentration of the heavy metal salts in the solution to be treatedcan vary widely, but is advantageously of a concentration between about1 and 20 grams of the heavy metal salt per liter of the aqueoussolution.

The solution to be treated can be contacted with the discrete particlesof the alltenyl aromatic resin containing the alkyl phosphate complexingagent by mixing the resin particles with the aqueous solution andthereafter separating the solution from the resin granules. In apreferred practice the resin particles are placed in a suitable vesselsuch as a vertical column to form a bed of the resin. The aqueoussolution containing the heavy metal salt to be extracted is contactedwith the resin by either upfiow or downflow of the aqueous solutionthrough the bed at suitable rates of flow, eg at from 0.1 to 10 gallonsof the aqueous solution per square foot of cross-sectional area of theresin bed per minute, and at room temperature or thereabout, althoughthe process can be carried out at elevated temperatures. Flow of theaqueous solution through the bed of the resin is continued until theresin has sorbed its capacity or substantially its capacity of the heavymetal salt from the solution. Thereafter, flow of the aqueous feedsolution is discontinued and the residual liquid surrounding the resingranules is drained or flushed from the bed.

The metal-containing resin granules can then be treated or washed withwater or an aqueous solution containing a mineral acid such as nitricacid, sulfuric acid or hydrochloric acid, to clute or displace thesorbed metal. The wash solution can be water or an aqueous solutioncontaining a mineral acid in a concentration between about a 0.1 normaland a 5 normal solution and/or containing a salting-out agent, e.g.sodium nitrate. By this procedure the alkenyl aromatic resin granulesare stripped of the sorbed heavy metal values and are regenerated to aform suitable for re-employment in another cycle of the operations.

The following examples illustrate ways in which the principle of theinvention has been applied, but are not to be construed as limiting itsscope.

EXAMPLE 1 In each of a series of experiments, a copolymer prepared bypolymerizing a mixture of monomers consisting of styrene, together witha mixture of approximately 55 percent by weight of divinylbenzene and 45percent of ethylvinylbenzene, in an aqueous suspension to form copolymerbeads cross-linked with divinylbenzene in amount as stated in thefollowing table, was reacted with surfuric acid to sulfonate the surfaceof the copolymer beads. The copolymer beads employed in the experimentswere of sizes between 50 and 100 mesh per inch as determined by U.S.Standard screens. A charge of 100 grams of the copolymer beads was mixedwith 500 grams of concentrated (98 percent) sulfuric acid maintained attemperatures between and C. on a steam bath. The resulting mixture wasstirred for a time as stated in the following table, then was removedfrom the steam bath and the copolymer separated from the sulfuric acidby filtering. The copolymer was immediately washed with a large volumeof water and was dried. The dried copolymer was analyzed to determinethe degree of sulf0nation. The procedure for determining the degree ofsulfonation was to measure the hydrogen ion content of a weighed portionof the sulfonated copolymer beads by potentiometric titration andcalculate the capacity in milliequivalents of hydrogen per gram of thedry sulfonated copolymer. A charge of approximately 60 grams of thesurface sulfonated copolymer beads was suspended in a mixture of 60parts by volume of tributylphosphate and 40 parts by volume ofperchloroethylene at a temperature of 80 C. to swell the copolymer. Theswelled beads were transferred to a 0.75-inch internal diameter steamjacketed glass column to form a bed of the copolymer beads 12 inchesdeep. The bed was maintained at a temperature of 100 C. while passingthe solvent mixture downiiow through the bed until the eflluent liquidwas of the same composition as the feed solution, i.e. until equilibriumwas established between the solvent mixture within the copolymer beadsand the solvent mixture surrounding the copolymer beads. The swelledcopolymer and liquid were removed from the column and were allowed tocool to room temperature. The copolymer was separated from the liquid byfiltering, then was washed with water to remove the solvent adhering tothe surfaces of the copolymer beads. The Washing was continued until thecopolymer beads were free from adhered solvent. The beads were dampdried by suction in the filter and were analyzed to determine thecomposition of the solvent mixture within the swelled copolymer beads. Acharge of 40 grams of the damp dried copolymer beads swelled with thesolvent mixture of tributyl phosphate and perchloroethylene was placedin a 0.5-inch internal diameter glass column to form a bed of thecopolymer beads. The column was held in a vertical position and wasfilled with an aqueous 2-normal sodium nitrate soloution to the toplevel of the bed of the copolymer beads. A feed solution consisting ofan aqueous solution containing 5 grams of uranium in the form of uranylnitrate, UO (NO 170 grams of sodium nitrate and 6.3 grams of nitricacid, per liter of the solution, was passed downflow through the bed ofthe copolymer beads at a rate of 2 ml. of the solution per minute. Theefliuent liquid was collected in successive 2 ml. fractions and wasanalyzed. The capacity of the swelled copolymer beads containing thesolvent mixture for absorbing uranyl nitrate from the aqueous feedsolution was determined by observing the break-through point of uranylnitrate in the eflluent liquid. The capacity is expressed in milligramsof uranium absorbed per gram of the solvent-swelled copolymer beads.Table I identifies the experiments and gives the percent by weight ofdivinylbenzene in the copolymer beads, the time in minutes for which thecopolymer beads were surface sulfonated and the degree of sulfonationexpressed as milliequivalents of hydrogen per gram of the dry sulfonatedbeads. The table also gives the composition of the swelled copolymerbeads in percent by weight of copolymer, percent by weight oftributylphosphate and percent by weight of perchloroethylene in theswelled beads. The table gives the capacity of the swelled copolymerbeads for absorbing uranyl nitrate from the aqueous feed solutionexpressed as milligrams of uranium percent of the solvent-swelledcopolymer beads. In the table the symbol In each of a series ofexperiments, a copolymer of 96.4 percent by weight of styrene, 1.6percent of ethylvinylbenzene and 2 percent of divinylbenzene, in theform of beads of sizes between 50 and mesh per inch as deterrnined byUS. Standard screens, which copolymer beads were surface sulfonated to adegree corresponding to 0.006 milliequivalent of hydrogen per gram ofthe dry resin was swelled with a liquid solvent as defined in thefollowing table employing procedure similar to that employed in thepreceding example. A charge of 40 grams of the solvent-swelled copolymerbeads was placed in a 0.5 inch internal diameter glass column to form abed of the resin. The copolymer was tested for its capacity to adsorburanyl nitrate from an aqueous solution employing procedure similar tothat employed in Example 1. Table II identifies the experiments andgives the composition of the liquid solvent employed to swell thecopolymer. The table also gives the composition of the swelled copolymerbeads in percent by weight of the copolymer and the solvent dissolvedtherein, and gives the capacity of the swelled copolymer beads forabsorbing uranyl nitrate from the aqueous solution, expressed asmilligrams of uranium per gram of the solventswelled copolymer.

A charge of a copolymer of 92.8 percent by weight of styrene, 3.2percent of ethylvinylbenzene and 4 percent of divinylbenzene, in theform of beads of sizes between 50 and 100 mesh per inch was surfacesulfonated, employing procedure similar to that employed in Example 1,to a degree corresponding to a capacity of 0.0036 milliequivalent ofhydrogen per gram of the copolymer. The surface sulfonated beads weresuspended in a mixture of 60 parts by volume of tributyl phosphate and40 parts by volume of perchloroethylene at room temperature for a periodof 3 hours. Thereafter, the copolymer beads were separated by filteringand were washed with water. The beads were analyzed and found to consistof 57 percent by weight of copolymer, 21 percent by weight of tributylphosphate and 22 percent by weight of perchloroethylene. Thesolvent-swelled copolymer beads had a capacity for adsorbing uranylnitrate from aqueous solutions of 46 milligrams of uranium per gram ofthe swelled copolymer beads when tested by procedure similar to thatemployed in Example 1.

EXAMPLE 4 A copolymer of styrene cross-linked with 2 percent by weightof divinylbenzene and surface sulfonated to a degree corresponding to0.006 milliequivalent of hydrogen per gram of the copolymer similar tothat employed in Example 2, was swelled in a solvent mixture consistingof equal parts by volume of tributyl phosphate and toluene. The swelledcopolymer was analyzed and found to consist of 51 percent by weight ofcopolymer, 30 percent by weight of tributyl phosphate and 19 percent byweight of toluene. The solvent-swelled copolymer beads had a capacityfor adsorbing uranyl nitrate from an aqueous solution of 64.5 milligramsof uranium per gram of the solvent swelled copolymer.

EXAMPLE 5 A copolymer of styrene cross-linked with one percent by weightof divinylbenzene in the form of particles of sizes between 50 and 100mesh per inch was surface sulfonated to a degree corresponding to 0.0051milliequivalent of hydrogen per gram of the resin employing proceduresimilar to that described in Example 1. The sulfonated copolymer beadswere swelled in a solvent consisting of a mixture of 40 parts by volumeof trioctyl phosphate and 60 parts by volume of perchloroethylene. Theswelled copolymer beads were analyzed and found to consist of 31 percentby weight of copolymer, 20 percent by weight of trioctyl phosphate and49 percent by weight of perchloroethylene. The solvent-swelled copolymerhad a capacity for adsorbing uranyl nitrate from an aqueous solution of24 milligrams of uranium per gram of the solvent-swelled copolymer whentested employing a solution of uranyl nitrate similar to that employedin Example 1.

EXAMPLE 6 A charge of 38 grams of solvent-swelled copolymer beadssimilar to that described in Run No. 3 of Table I, was placed in a 0.5internal diameter glass tube held in a vertical position to form a bedof the beads. The column was filled to the top level of the copolymerbeads with an aqueous 2-normal sodium nitrate solution. The bedcontained 45 ml. of the solvent-swelled copolymer beads and 17 ml. ofaqueous liquid surrounding the beads. A feed solution consisting of anaqueous solution containing 10.55 grams of uranyl nitrate 170 grams ofsodium nitrate and 1.6 grams of nitric acid per liter of the solutionwas fed to the bed at a rate of 2 m1. of the solution per minute, andpassed downflow through the bed of the copolymer beads, whilewithdrawing eflluent liquid from the bottom of the column at a ratecorresponding to the rate of feed to the bed. The effiuent liquid wascollected in successive 5 ml. fractions. The fractions were analyzed todetermine the amount of uranyl nitrate therein. After thesolvent-swelled beads had absorbed their capacity of uranyl nitrate,feed of the solution to the bed was discontinued and the liquidsurrounding the copolymer beads was flushed therefrom with water. Thefeed of water to the bed was continued at a rate of 2 ml. per minute toelute the sorbed uranyl nitrate from the swelled copolymer beads. Thesorbed uranyl nitrate was quantitatively eluted from the solventswelledcopolymer beads with 60 ml. of water. The operations of adsorbing theuranyl nitrate from the feed solution in the solvent-swelled copolymerbeads containing tributyl phosphate and elution of the sorbed uranylnitrate from the solvent-swelled copolymer beads by washing with waterwas repeated over a series of three cycles with substantially similarresults.

EXAMPLE 7 A copolymer of 92.8 percent by weight of styrene, 3.2 percentof ethylvinylbenzene and 4 percent of divinylbenzene, in the form ofbeads of sizes between 30 and 50 mesh per inch as determined by USStandard screen, was sulfonated to a degree corresponding to 0.006milliequivalent of hydrogen per gram of the sulfonated copolymer beadsemploying procedure similar to that described in Example 1. Thesurface-sulfonated copolymer beads were swelled in a solvent mixtureconsisting of 60 parts by volume of tributyl phosphate and 40 parts byvolume of perchloroethylene, then were Washed with water. The swelledcopolymer beads were analyzed and found to consist of 55 percent byweight copolymer, percent tributyl phosphate and percentperchloroethylene. A charge of 58.5 ml. of the solvent-swelled copolymerbeads was placed in a vertical 0.5 inch internal diameter glass tube toform a bed of the copolymer beads. The column was filled with an aqueousZ-normal solution of sodium nitrate to the top level of the bed of thebeads. Thereafter, 200 ml. of an aqueous solution containing 10.55 gramsof uranyl nitrate (UO (NO -6H O), 31.2

grams of ferric nitrate (Fe(NO -6H O) and 252 grams of nitric acid perliter of the solution was fed to the column and passed downflow throughthe bed of the copolymer beads at a rate of one milliliter per minute.This was followed by the feed of 30 ml. of an aqueous 4-normal nitricacid solution to the column, after which water was fed to the column toelute the sorbed uranyl nitrate from the solvent-swelled copolymerbeads. Effiuent liquid was withdrawn from the bottom of the column at arate corresponding to the rate of feed to the column. The eilluentliquid was collected in successive 10 ml. fractions and was analyzed.The solvent-swelled copolymer beads selectively sorbed the uranylnitrate from the aqueous feed solution. The ferric nitrate remained inthe solution surrounding the copolymer beads as was determined byanalysis of the effluent liquid. The sorbed uranyl nitrate was elutedfrom the solventswelled copolymer beads by the washing with water, and94 percent of the sorbed uranyl nitrate was recovered in 120 ml. of theefiiuent liquid.

EXAMPLE 8 A charge of 50 ml. of a solvent-swelled copolymer compositionsimilar to that described in Run No. 4 of Table 1 was placed in a 0.5inch internal diameter glass tube to form a bed of the copolymer beads.The column was filled with an aqueous 2-normal solution of sodiumnitrate to the top level of the copolymer beads. A volume of 190 ml. ofan aqueous feed solution containing 23.75 grams of thorium nitrate,Th(NO -4H O, 2.11 grams of uranyl nitrate, UO (NO -6H O, 176 grams ofsodium nitrate and 6.3 grams of nitric acid per liter of the solutionwas fed to the column at a rate of 2 ml. of the solution per minute andwas placed downflow through the bed of the copolymer beads. This wasfollowed by the feed of 160 ml. of an aqueous solution containing 170grams of sodium nitrate and 6.3 grams of nitric acid per liter of thesolution, after which water was fed to the column to elute the sorbedmetal salts from the solvent-swelled copolymer. Effluent liquid waswithdrawn from the bottom of the column and was collected in successivefractions. The fractions were analyzed. Table III identifies thefractions and gives the total volume of the efiluent liquid. The tablealso gives the concentration of the uranium and thorium in thefractions, expressed as grams of said metals per liter of the effluentliquid.

Table III Concentration of metals Efiluent in efllucnt liquid FractionNo. liquid volume, ml.

Th, gm./l. U, gin/1.

30 40 4 50 9.6 10.3 10. 7 10. 9 ll. 0 100 11.0 200 10.9 210 10.7 220 9.5 240 6. l 260 3.7 280 2. 3 300 l. 6 320 1. l 340 0.75 0.05 360 0. 4 0.2370 0.3 0.35 380 0. 2 4. 0 390 0. 1 7. 7 3. 6 1. 9 0.8 0. 3

As shown in the above table, the uranyl nitrate was selectively sorbedby the solvent-swelled copolymer beads and was eluted from the beads bywashing with water.

FIG. 1 of the drawing is an elution curve showing the concentration ofthe metal salts in the efiluent liquid.

EXAMPLE 9 A charge of 39 m1. of a solvent-swelled copolymer compositionsimilar to that described in Run No. 2 of Table I was placed in a 0.5inch internal glass tube to form a bed of the swelled copolymer beads.The column was filled with an aqueous 2-normal sodium nitrate solutionto the top level of the copolymer beads. A volume of 85 m1. of anaqueous solution containing thorium nitrate, Th(NO -4H O, in aconcentration corresponding to a 0.0432 molar solution, yttrium nitrate,Y(NO -6H O, in a concentration corresponding to a 2-normal solution andnitric acid in a concentration corresponding to a 0.1 normal solutionwas fed to the column at a rate of 2 ml. of the solution per minute andwas passed downfiow through the bed of the solvent-swelled copolymerbeads. After feed of this solution, the bed was rinsed with 27 ml. of anaqueous solution containing 170 grams of sodium nitrate and 6.3 grams ofnitric acid per liter of solution, then was washed with water to elutethe sorbed metal values from the copolymer beads. The feed of all of thesolutions to the bed was at a rate of 2 ml. of the solution per minute.Efiluent liquid was withdrawn from the bottom of the column at a ratecorresponding to the rate of feed to the column. The eflluent liquid wascollected as successive fractions and was analyzed'. Table IV identifiesthe fractions and gives the volume of the efiluent liquid inmilliliters. The table also gives the concentration of the yttriumnitrate in the efiluent liquid expressed as the rato of grams of yttriumper liter of the eflluent liquid divided by the grams of yttrium perliter of the feed solution. The thorium nitrate in the efiiuent liquidis expressed in similar units.

Table IV Concentration of metals in efliuent liquid, Ei-Huent gm./literof efiiuent Fraction No. liquid, ml. +gm./liter of feed Y Th OwnncnPPPPFl-FP ooowceeecemoo As shown in the above table, complete separationof the thorium nitrate from the yttrium nitrate was obtained. FIG. 2 isan elution curve showing the concentration of the metal salts in theefiluent liquid and plotted from the data in Table IV.

EXAMPLE 10 A copolymer of 92.8 percent by weight of styrene, 3.6 percentof ethylvinylbenzene and 4 percent of divinylbenzene in the form ofbeads of sizes between 100 and 200 mesh per inch as determined by U.S.Standard screen and having the surfaces of the beads sulfonated to adegree corresponding to 0.0036 milliequivalent of hydrogen per gram ofthe resin was swelled in a solvent mixture consisting of tributylphosphate and perchloroethylene,

then was washed with water and analyzed. The solventswelled copolymerbeads were found to consist of 55 percent by weight of copolymer, 20percent by weight of tri butyl phosphate and 25 percent by weight ofperchloroethylene. A charge of 88 ml. of the solvent-swelled copolymerbeads was placed in a 0.5 inch internal diameter glass tube to form abed of the copolymer beads. The tube was filled to the top level of thecopolymer beads with an aqueous solution of IO-normal ammonium nitrate.A volume of 10 ml. of an aqueous 0.1 normal nitric acid solutioncontaining yttrium nitrate and ferric nitrate in concentrationscorresponding to 40 grams of yttrium and 71 grams of iron per liter ofthe solution was fed to the bed at a rate of 2 ml. of the solution perminute, thereby displacing an equal volume of liquid from the bed.

This was followed by the feed of 10 ml. of an aqueous 10-normal ammoniumnitrate solution to the bed at the same rate, after which water was fedto the bed at a rate of 2 ml. per minute. The eflluent liquid from thebottom of the bed was collected as successive 2 ml. of fractions, andwas analyzed. Good separation of the yttrium nitrate from the ferricnitrate was obtained.

What is claimed is:

1. A composition of matter suitable for the recovery of heavy metalvalues from aqueous solutions containing the same which comprisesdiscrete gel-like water-insoluble organic solvent-containing granules ofa copolymer of from 92 to 99.5 percent by weight of at least onemonoalkenyl aromatic hydrocarbon having the general formula:

wherein Ar represents an aromatic hydrocarbon radical of the benzeneseries and R represents a member of the group consisting of hydrogen andthe methyl radical, and from 8 to 0.5 percent by weight of a divinylaromatic hydrocarbon, said copolymer granules containing on the surfacethereof substituent hydrophile group of the formula SO X wherein Xrepresents a member of the group consisting of hydrogen and a metal, inamount corresponding to from 0.001 to 0.150 milliequivalent of hydrogenion per gram of said dry surface-sulfonated copolymer, which copolymergranules are swelled with a Water-immiscible organic liquid comprising atrialkyl phosphate having the general formula:

wherein R, R and R" each independently represent an alkyl radicalcontaining from 4 to 8 carbon atoms, as complexing agent for heavy metalvalues, and an organic liquid solvent which swells said alkenyl aromaticresin, in proportions corresponding to from 5 to percent by volume ofthe organic swelling agent and from 95 to 20 percent by volume of thetrialkyl phosphate.

2. A composition as claimed in claim 1, wherein the copolymer is aresinous copolymer of a predominant amount of styrene with lesseramounts of ethylvinylbenzene and divinylbenzene.

3. A composition as claimed in claim 1, wherein the Water-immiscibleorganic liquid is a mixture of tributyl phosphate and perchloroethylene.

4. A composition as claimed in claim 1, wherein the water-immiscibleorganic liquid is a mixture of trioctyl phosphate and toluene.

No references cited.

1. A COMPOSITION OF MATTER SUITABLE FOR THE RECOVERY OF HEAVY METALVALUES FROM AQUEOUS SOLUTIONS CONTAINING THE SAME WHICH COMPRISESDISCRETE GEL-LIKE WATER-INSOLUBLE ORGANIC SOLVENT-CONTAINING GRANULES OFA COPOLYMER OF FROM 92 TO 99.5 PERCENT BY WEIGHT OF AT LEAST ONEMONOALKENYL AROMATIC HYDROCARBON HAVING THE GENERAL FORMULA: